A system of the above-described type is disclosed in published German application DE-OS No. 25 49 586. In order to generate control signals of sufficient amplitude, the AC generator of this prior art system and its associated coil must be relatively large so that it is difficult to accommodate it in the distributor housing. Further, its construction is relatively expensive both because of the use of relatively expensive materials and the required precision. It is a further disadvantage of the known system that the peak value of the AC control signal increases with increasing engine speeds. Therefore, special precautions must be taken to assure adequate operation at low engine speeds.